This invention relates to a knocking sensor for an internal combustion engine and more particularly to an improved knocking sensor that will give accurate signals regardless of variations in the sensor internal conditions.
The use of knock sensors for internal combustion engines is becoming more common. One of the uses for such knock sensors is to control the ignition timing so as to provide optimum ignition timing under all conditions while at the same time preventing the damage to the engine by knocking. An arrangement wherein such a knock sensor is employed is shown in U.S. Pat. No. 4,606,315, issued Aug. 19, 1986, entitled "Ignition Control System For Internal Combustion Engine" and assigned to the assignee of this application.
Knock sensors are of a wide variety of types and many of them operate to provide a signal indicative of a knocking condition by comparing an instantaneous signal with a reference signal. One way that this is done is that the knock sensor memorizes a reference signal which existed slightly before the time of ignition and compares this with the actual signal received at all times. The use of such reference signals is advantageous due to the variation of the internal components of the sensor which may occur with time or to filter out conditions such as external or internal noise. However, when such a reference signal is employed, there is a danger that the reference signal will be set as the signal which indicates actual knocking, for example, if the reference signal is set at the time when ignition or knocking actually occurs, and thus actual knocking of the engine will not be sensed.
It is, therefore, a principal object of this invention to provide an improved knock sensor for an internal combustion engine.
It is another object of this invention to provide a knock sensor for an internal combustion engine that will provide an accurate signal and yet which is quite similar to the prior art type of construction.